The invention relates to compounds, methods and kits for the determination of sirolimus compounds such as, for example, rapamycin or derivatives thereof, in samples, such as patient samples, known or suspected to contain such sirolimus compounds.
The body relies upon a complex immune response system to distinguish self from non-self. At times, the body's immune system must be controlled in order to either augment a deficient response or suppress an excessive response. For example, when organs such as kidney, heart, heart-lung, bone marrow, and liver are transplanted in humans, the body will often reject the transplanted tissue by a process referred to as allograft rejection.
In treating allograft rejection, the immune system is frequently suppressed in a controlled manner with drug therapy. Immunosuppressant drugs are carefully administered to transplant recipients in order to help prevent allograft rejection of non-self tissue. Two most commonly administered immunosuppressive drugs to prevent organ rejection in transplant patients are Cyclosporine (CSA) and FK-506 (FK). Another drug that finds use as an immunosuppressant in the United States and other countries is sirolimus, also known as rapamycin. Derivatives of sirolimus are also said to be useful as immunosuppressants. Such derivatives include, for example, Everolimus, and the like.
Rapamycin is a macrocyclic trione antibiotic produced by Streptomyces hygroscopicus. Rapamycin is structurally related to the immunosuppressant FK-506 (Tacrolimus) but mechanistically different. Rapamycin has anti-candidal, anti-proliferative and anti-tumor activity. Rapamycin also dampens autoimmune reactions (SLE, adjuvant arthritis, allergic encephalomyelitis). Rapamycin is a potent immunosuppressant that inhibits T and B cell activation by blocking cytokine-mediated events, and inhibits growth factor mediated cell proliferation.
The side effects associated with rapamycin can be controlled in part by carefully controlling the level of the drug present in a patient. Because the distribution and metabolism of rapamycin can vary greatly between patients and because of the wide range and severity of adverse reactions, accurate monitoring of the drug level is essential.
Several derivatives of rapamycin have been prepared in the hope of finding an agent that possesses all of the desired immunosuppressive properties of rapamycin, but whose use results in less side effects. Such derivatives include the preparation of oxime derivatives of rapamycin (U.S. Pat. Nos. 5,672,605; 5,373,014; 5,023,264 and 5,378,836).
Rapamycin and its derivatives are being assessed in a number of clinical trials around the world as immunosuppressive agents. In the trials, therapeutic drug monitoring (TDM) of plasma levels of rapamycin is recommended for all patients, and especially pediatric patients and those with hepatic impairment. TDM is also recommended when potent inducers or inhibitors of the enzyme CYP3A4 are co-administered. In addition, if rapamycin or its derivative is concomitantly administered with cyclosporin, TDM is recommended because pharmacokinetics are altered during drug co-administration. For example, if rapamycin is administered concomitantly with cyclosporin rather than administered four hours apart, rapamycin trough levels increase. For this reason, as well as to limit certain side effects, TDM should allow for better clinical results in selected cases.
Therapeutic monitoring of concentrations of rapamycin and related drugs in blood is required to optimize dosing regimes to ensure maximal immunosuppression with minimal toxicity. Although rapamycin is a highly effective immunosuppressive agent, its use must be carefully managed because the effective dose range is narrow and excessive dosage can result in serious side effects. On the other hand, too little dosage of rapamycin can lead to tissue rejection.
There is, therefore, a continuing need to develop fast and accurate diagnostic methods to measure levels of sirolimus compounds such as rapamycin or a derivative thereof in patients.